Use sockets to broadcast morse progress.

morse/lib/morse_server.ex

@@ -8,27 +8,41 @@ defmodule MorseServer do
   end
 
   def start_link do
-    GenServer.start_link(__MODULE__, nil, name: __MODULE__)
+    GenServer.start_link(__MODULE__, {nil, 0}, name: __MODULE__)
   end
 
   def start_morse do
     GenServer.call(__MODULE__, :start)
   end
 
+  def update_progress(progress) do
+    GenServer.cast(__MODULE__, {:progress, progress})
+  end
+
   @impl true
   def init(state) do
     {:ok, state}
   end
 
   @impl true
-  def handle_call(:start, _from, pid) do
+  def handle_call(:start, _from, {pid, _progress} = state) do
     cond do
       pid == nil or not Process.alive?(pid) ->
         pid = spawn(&MorseSignaler.signal/0)
-        {:reply, :ok, pid}
+        {:reply, :ok, {pid, 0}}
 
       true ->
-        {:reply, {:error, :already_started}, pid}
+        {:reply, {:error, :already_started}, state}
     end
   end
+
+  @impl true
+  def handle_cast({:progress, new_progress}, {pid, progress}) do
+    broadcast_progress(new_progress)
+    {:noreply, {pid, new_progress}}
+  end
+
+  defp broadcast_progress(progress) do
+    UiWeb.Endpoint.broadcast("morse:progress", "update", %{value: progress})
+  end
 end

morse/lib/morse_signaler.ex

@@ -23,13 +23,23 @@ defmodule MorseSignaler do
     {:ok, gpio} = GPIO.open(relay_pin(), :output)
     GPIO.write(gpio, @off)
     Process.sleep(@sleep_start)
-    signal_sentence(gpio, String.graphemes(secret_code()))
+    update_progress(gpio, String.graphemes(secret_code()))
+  end
+
+  # Update progress for clients, and signals the rest of the sentence.
+  defp update_progress(gpio, symbols) do
+    100 - length(symbols) / String.length(secret_code()) * 100
+    |> MorseServer.update_progress()
+    if symbols != [] do
+      signal_sentence(gpio, symbols)
+    end
   end
 
   # Signal a whole sentence of symbols with GPIO.
   defp signal_sentence(gpio, []) do
     GPIO.write(gpio, @off)
     GPIO.close(gpio)
+    update_progress(gpio, [])
     :ok
   end
 
@@ -50,7 +60,7 @@ defmodule MorseSignaler do
   defp signal_sentence(gpio, [" " | rest]) do
     Process.sleep(@sleep_pause)
 
-    signal_sentence(gpio, rest)
+    update_progress(gpio, rest)
   end
 
   defp signal_sentence(_gpio, [symbol | _rest]) do